Questions tagged [hvac]

(Heating, Ventilating, and Air Conditioning) For questions about installing, repairing, and troubleshooting HVAC systems.

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Attic Fan coil short cycles in heat mode

My attic fan coil unit (MBX-HW) fan will short cycle in heat mode. On for 20sec off for 20sec. Worked fine in cool mode last Summer. Replaced the filter, thermostat replaced 2 years ago. The heat ...
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1answer
29 views

One Furnace, Dual Zones — Install Sensi on each?

Just bought a new (<6 years old) house and it's two stories, but only has a single furnace in the attic and a single condenser outside. However, there are two thermostats that work (semi) ...
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Heating system cycling

My heating system is power cycling because the heat exhaust temperature sensor is tripping. When I turn the intake gas valve closed a bit, the system will stay on for longer but it's still does some ...
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28 views

Keep Purging Heat Every Two Weeks

I have a three zone hydronic heating system. For some reason this year I have had to purge my system every 2-3 weeks because I keep getting air in the pipes. I know this because I hear water start to ...
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1answer
12 views

One of two Nest Thermostats won't run Fan Only, fan runs with heat though

We've got two Nest Learning Thermostats (3rd Gen) running two separate heating and cooling units in an office. They both work fine for heating and cooling, with one exception: one unit will not turn ...
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3answers
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(SOLVED) What is a whining, high pitch sound coming from my furnace when heat kicks in

EDIT: SOLVED. IT WAS THE FLEX CONNECTOR. THANKS EVERYONE. My gas furnace makes a high-pitched whining sound when the burners turn on (when I can see fire). A repair man came and told me it may be that ...
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0answers
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HOW TO WIRE AN EMERSON BLOWER MOTOR [closed]

I HAVE AN OLD KA55HXJGA-5130 PSC BLOWER MOTOR. HOW CAN I GET A WIRING DIAGRAM TO HOOK IT UP ? THE MOTOR SPECS ARE: 1/4HP, 208/240V, 1050RPM, 4SPD, MFG NO K81 8, PT NO 20169-01, 7 WIRES.
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1answer
17 views

Amana furnace discharge vent seems clogged

My furnace starts out very slowly trying to put out hot air maybe 2 to 3 hours. I think maybe my discharge vent may be clogged but its on a slippery roof and about 30 foot of PVC so how would I clean ...
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1answer
40 views

Where should my humidistat on my whole house humidifier be located

I have a Trion cm200 installed on my air handler up in the attic of my house. Toward the end of 2018 I had an entire electric system installed in my house (duct work, air handler and outside ...
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5answers
3k views

Does a thermostat need to be connected to the fuse box? My builder says no?

I just purchased a home, and was in the process of replacing the thermostats with Nests. I flipped off all the circuits in the fuse box, and the thermostat on the first floor powered off. However, the ...
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4answers
136 views

Considerations for installing a high efficiency furnace in my attic?

I live in Upstate NY and in the winter it gets below 0° F. I currently have baseboard water heating throughout my home. Prior to this I believe there was a gravity furnace which supplied the house ...
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Tempstar 2 stage furnace restarting every 7 minutes - not going into high

I have a tempstar 9MPT model based furnace. Also sold under a number of other brands - comfort air, etc. It is a two stage heating with a PSC motor high efficiency furnace. After about 7 minutes of ...
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3answers
71 views

Re-route HVAC around basement window?

Working on my basement and this part of the HVAC covers the corner of that window. Can it be re-routed or reconfigured to fit around the window better? It connects to the kitchen upstairs.
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2answers
42 views

What should I do with the airflow in a sealed off conditioned crawlspace

First and foremost thanks ahead of time for everyone's help :) I am in the process of finishing my basement and had some questions/concerns about "what to do with the air" in my crawlspace. In my ...
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1answer
19 views

HVAC Furnace - Adding C Wire to Older Wiring Style

Hello! Trying to add a smart thermostat to an old system (currently running a mercury thermostat on it). There is an extra wire (orange) which you can see both inside the thermostat and also in the ...
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0answers
19 views

Thermostats with or without variable temperature differential (swing)

I am looking at replacing my thermostat, and don't really need or want one with geosync. I am thinking of the honeywell RTH9585wf. Currently I have a lux that is not wifi but programmable. It ...
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2answers
28 views

Tempstar (ICP) furnace short cycle (runs 10 -15 minutes) then repeats

I have a tempstar (ICP) furnace put in when the house builder built the house. Model is N9MPD075F12A2. Installed late 2009. This problem only happens with the furnace not the AC. When calling for ...
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2answers
37 views

HVAC Preventative Maintenance

Is it necessary to add bleach or vinegar monthly to HVAC line when system is not in use, mainly when air conditioning and heat are not necessary.
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0answers
18 views

AC compressor runs with heat on. NOT a heat pump

My AC compressor recently started running whenever the heat kicks on. It is not a heat pump. The compressor is a Nordyne fs3ba-036ka. I haven't done anything to the system aside from changing filters ...
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0answers
25 views

How to wire Aprilaire 600a to older furnace

I need help wiring an Aprilaire 600a humidifier yo my older oil furnace (from 1998). I thought I had followed the wiring instructions properly, but the digital humidistat is giving me an error code (...
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0answers
24 views

Furnace sometimes does not start

I have a 5 year old Broan furnace model M7RL 072A AW downflow condensing gas furnace. Here's the furnace startup sequence: pump runs ignitor glows hear the click of the gas valve opening fires up ...
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2answers
25 views

A/C compressor connection to the house not sealed anymore. How do I fix it?

The A/C compressor that sits outside our home had a sealed connection to the house (pretty new, 3 years old), and it seems a "gasket" was created with silicone. However, the soil underneath the ...
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1answer
45 views

Intermittent sewage smell from air ducts

My home is two stories, 5100 sq feet, and was built in 1990. I have a septic system, radon mitigation, and central forced air. This has gone on for two winters now, but not before that. The second ...
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0answers
17 views

I changed my thermostat and now my outside unit won’t turn on

I have a trane heat pump and A/C unit outside and a trane unit inside. I had to replace my thermostat because the one I had, didn’t have emergency heat option on it. I turned off the breaker and ...
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1answer
46 views

Low Voltage C-Wire at Thermostat

Looking to install an ecobee thermostat and decided to measure my common wire before unhooking anything. I tested the R, C wires and see they are only reading 14v, whereas R,Y, and R,W are reading 28v....
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1answer
46 views

Air conditioner locating c wire on old unit

Hi guys I'm trying to figure out I'm using a dual heat and cool thermostat so i decided to get myself a smart thermostat and want to connect both thermostats into 1 but I'm having trouble location the ...
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1answer
54 views

Just put calcium carbonate rocks in my condensate water pump or buy a whole condensate kit?

Can I just put some calcium carbonate rocks in my Beckett water pump (see photo of pump, below) to neutralize the HVAC condensate, or do I have to spring for a whole assembly, like this (The refills ...
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1answer
27 views

how to test to see if a humidistat temperature sensor is working

I have an April Air 600 humidistat with an outside temperature sensor. What is the procedure to test a temperature sensor to see if it is working.
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0answers
13 views

Does manual operation of a Taco 570 series zone valve operate the boiler?

I have a home with multiple zones with the valves mentioned in the question. The documentation (http://www.taco-hvac.com/uploads/FileLibrary/100-3.pdf) isn't clear about whether contact 3 is ...
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1answer
53 views

Wiring HVAC for smart thermostat

I'd like to install a smart thermostat in place of my old mercury coil thermostat. The old thermostat controls both heat and AC - it uses only 4 wires, the new clearly requires 5. Wiring to the ...
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0answers
12 views

Nest Thermostats: Balancing temperatures between zones

So, I'm wondering if there's a way that I can program my Nest thermostats to help moderate temperature disparities between my first and second floors. Here's the situation: I have forced air from a ...
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1answer
113 views

No C Wire Nest Thermostat

I just installed a nest thermostat. The previous thermostat did not have a C wire attached. It G, RC, (RH Jumper), Y and W. When I hooked up the nest thermostat it was short cycling the blower fan ...
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1answer
37 views

Is a pulse width modulating thermostat compatible with a W2 auxillary heating (Nest compatibility question)

I have the wiring configuration for a RHEEM thermostat Pictured Below. On it, there is a "V" wiring connection which according to the manufacturer is for "Pulsed width modulation" type heating. On the ...
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1answer
286 views

Why is there a 1/2-inch hole drilled in my heater exhaust?

I have a Carrier high efficiency furnace which uses 2-inch PVC pipes to pull in combustion air from outside and exhaust the combustion gasses back outside (through a concentric vent, but that's not ...
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1answer
36 views

Purging boiler with just one drain valve

I have read through how to purge a zone, but I still have a question. I don't have individual drain valves on each zone. So I am unsure what the process would be in order to purge a zone. And to ...
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0answers
35 views

Very Old thermostat with TR wires

I want to buy a new smart thermostat, but am confused on the old wiring. I have single zone 120year old gas boiler (converted from coal, then oil, now gas). No cooling. The old honeywell thermostat is ...
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0answers
37 views

Seal old ductboard from inside with duct mastic?

For the next few days, I have what appears to be an opportunity to easily and cheaply make a small improvement to the overall airtightness (or nearly complete lack thereof) of my house's 40 year old ...
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2answers
69 views

What steps should I take to prepare for using a thermal camera?

I plan on renting a thermal camera to detect heat loss (e.g., missing insulation, leaks in HVAC) and water damage. Outside temperatures are getting down to freezing at night but are mid-40s during the ...
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0answers
17 views

Honeywell Y8150A1017 Ventilation System

We recently bought a house in North Carolina and the HVAC system has HONEYWELL Y8150A1017 fresh air ventilation system which seems to call for fresh air exchange quite often. In the winter, the air ...
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0answers
24 views

Suggestions on where to relocate a wall register I'm enclosing in a closet? (with labeled floor plan attached). Thank you!

I'm looking for some suggestions on where to relocate the HVAC wall register (shown in red), as I am planning to enclose it in a closet. It comes from 3x7 rectangular duct into the 2x4 wall and rests ...
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1answer
14 views

What is the proper replacement igniter for my York furnace?

I replaced one of these before on another unit but the part number was printed on the igniter. This one is not so, being ignorant to HVAC I just want to make sure I get the appropriate part. York ...
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0answers
32 views

HVAC duct sizing

I have a 4 ton American Standard electric forced air furnace (with no A/C - just heat) with a single speed blower motor, circa 2006. My supply main trunk is 12"x20". The return side of the system ...
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1answer
29 views

Can’t find breaker for AC unit

I have 2 AC units and I’m installing Ecobee thermostats. The upstairs unit is on the main panel and I was able to turn it off and install the thermostat. I turned off the main breaker and the ...
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0answers
16 views

Water not circulating through baseboards

2 zone (1 radiant floor, 1 baseboards) hot water heating system. Radiant floor (t’d off main feed) seems to be working fine. None of the baseboard loops are hot, and the pipe was hot before the ...
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2answers
41 views

Gas Forced Hot Air seems to be blowing extremely hot air

Gas forced hot air. The floor registers are hot to the touch after 6 minutes heat running, if left hand on register would burn quickly. Don't remember it being this hot before.
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2answers
55 views

Theory: How do thermostats without a “C” common wire get powered?

My simple question is: When a thermostat has four wires: white, red, green, and yellow, the red is for 24V (AC?) and the white/green/yellow are for heat/fan/cooling. The role of the thermostat is to ...
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1answer
26 views

Should whole house humidifier be draining when heater/fan is off?

I have an Aprilaire 700 whole house humidifier with a manual mode humidistat on the return. I noticed that the unit was draining water even when the heater/fan was off. Is this expected? I just hear ...
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1answer
22 views

Furnace shutoff switch outlet only hot when furnace is running

I have an old Aprilaire 700 powered by the 110v outlet on the side of my furnace. I recently replaced the old humidistat with a newer Aprilaire 60 Digital. This humidistat comes with the blower ...
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1answer
36 views

Help with a Nest E install on a old HVAC system

Hello I am trying to replace this thermostat with a Nest E but this has proven more complicated than I thought: I plugged all the cables to the nest adapter and figured that the blue wire which wasn'...
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1answer
33 views

Can I remove this HVAC damper?

Is is possible to remove this damper? It looks like there are special kind of screws about an inch above but I'm not sure how those would come out. If I can't be remove could it be cut out? I have an ...